php - 在 MySQL 中 INSERT INTO ... ON DUPLICATE KEY UPDATE 的正确语法是什么？

Question

我的表结构(MySQL/每一个都与下面相同)

+-------+--------------+------+------+-------------------+
| Field | Type         | Null | Key  | Default           |
+-------+--------------+------+------+-------------------+
| id    | int(11)      | NO   | PRI  | AUTO INCREMENT    | 
| lesson| varchar(255) | NO   |      | LESSON_NAME       | 
| exam  | char(50)     | NO   |UNIQUE| NO DEFAULT        |
| quest | text         | NO   |      | NO DEFAULT        |
| answer| text         | NO   |      | NO DEFAULT        |
| note  | text         | NO   |      | NO DEFAULT        |
+-------+--------------+------+------+-------------------+

我正在发布一些值以通过 ajax ($post) 添加此表 - PHP 5.0
在 database.php 中有一个函数可以获取发布的数据并添加到表中

function update_table ($proper_table, $name, $question, $answer, $note) {
$sql = "INSERT INTO $proper_table (id, lesson, exam, quest, answer, note) VALUES ('', '', $name, $question,$answer,$note) ON DUPLICATE KEY UPDATE exam = $name, quest = $question, answer = $answer, note = $note";
$result= mysql_query($sql)or die(mysql_error());
}

$proper_table 变量被另一个变量取用，将这条记录添加到正确的表中。
(注意:原始表字段和变量不同(土耳其语)，为了更容易理解，我翻译成英语，但语法与您看到的相同。)
问题:我想检查是否存在考试字段相同的记录，然后所有这些变量都将用于更新此记录，否则让函数将此记录作为新记录放入适当的表中。
但是我收到如下错误

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 

是否有任何错误的编码？什么是解决方案？
现在谢谢...

Answer 1

function update_table ($proper_table, $name, $question, $answer, $note) {
    $sql = "INSERT INTO $proper_table (lesson, exam, quest, answer, note) VALUES ('', '$name', '$question','$answer','$note') ON DUPLICATE KEY UPDATE quest = VALUES(quest), answer = VALUES(answer), note = VALUES(note)";
   $result= mysql_query($sql)or die(mysql_error());
}

只是打破这个，我会详细说明变化

$sql = "INSERT INTO $proper_table 

// Removed the PK (primary key) AI (auto increment) field - don't need to specify this
(lesson, exam, quest, answer, note)     

// Likewise removed PK field, and added quotes around the text fields
VALUES ('', '$name', '$question','$answer','$note')    
ON DUPLICATE KEY UPDATE 

// If you specify VALUES(fieldName) it will update with the value you specified for the field in the conflicting row
// Also removed the exam update, as exam is the UNIQUE key which could cause conflicts so updating that would have no effect
quest = VALUES(quest), answer = VALUES(answer), note = VALUES(note)";